Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$94.56	9.649%	$103.6841	$103.68	$103.70	$103.70
Purchase #2	$79.89	12.150%	$89.5966	$89.60	$89.60	$89.60
Purchase #3	$64.44	5.398%	$67.9185	$67.92	$67.90	$67.90
Purchase #4	$55.86	13.246%	$63.2592	$63.26	$63.25	$63.30
Purchase #5	$120.97	12.573%	$136.1796	$136.18	$136.20	$136.20
Purchase #6	$182.31	10.483%	$201.4216	$201.42	$201.40	$201.40
Purchase #7	$151.58	13.806%	$172.5071	$172.51	$172.50	$172.50
7 purchase totals =	$749.61		$834.5667	$834.57	$834.55	$834.60